1. Field of the Invention
This invention relates to apparatus for dispensing powders and other finely divided material into receptacles such as valved bags, and more particularly to an automatic bag filling machine which uses vacuum within a bag enclosing shroud to draw finely divided material into the bag in a series of increments to fill the bag more compactly.
2. Brief Description of the Prior Art
Through the years, a variety of different filling methods and machines for filling receptacles have been developed and have to varying degrees met with satisfactory acceptance in the receptacle filling industry. Although a number of acceptable proposals and machines have been developed for the handling of ordinary particulate materials, it is recognized that special problems are encountered in connection with the handling and dispensing of very finely divided or powdered materials.
With the very finely divided materials as referred to above, there is a tendency for the material to become fluffy by reason of air entrained in the powder. Whereas such entrained air may serve a useful purpose in facilitating freer flow of the material through the dispensing machine to the receptacle being filled, it is a distinct drawback from the standpoint of achieving the desired degree of material compaction within the filled receptacle. Removing this entrained air to compact the material presents a real problem in filling the receptacle with these powdered materials.
In the past, one suggested solution to compacting finely divided material by freeing it of air which becomes entrained between the powder particles has been to subject the receptacle during filling to rapid vibration. Under this filling method, as the particles tend to settle down, material is added to the receptacle until the receptacle contains the desired weight of material for its particular size. Whereas this filling method has been and is presently being used, it has a distinct disadvantage in that it may require a period of several hours of continuous receptacle vibration and repeated material additions to fill a drum with the desired weight of powdered material as for example in the case where silica gel or carbon black is being dispensed. In comparison with this length of time required for vibratory filling, the present invention can achieve the same degree of material compacting in filling the same size receptacle in a matter of minutes.
As a further problem encountered in the handling and dispensing of very finely divided powders, the characteristic of such powders to become dispensed in the atmosphere surrounding the filling machine and thereafter settle on the machine parts and areas adjacent the machine has been recognized as a definite problem in the development of filling machines. Accordingly, it is of the utmost importance that a filling machine for use in handling such finely divided powders to be constructed to reduce to a minimum the escape of powders either from the machine mechanism itself or from the receptacle as it is being filled.
The construction of the filling machine of the instant invention and its mode of operation have been developed to possess the required characteristics for the handling of finely divided powders. As a further advantage of the filling machine described in detail hereinafter, its automatic operation, commencing from the time of introduction of the bag to be filled into the shroud and continuing through the completion of the bag filling cycle, contributes to reducing the chance for escape of powdered material into the surrounding atmosphere.
The bag filling apparatus of the present invention is a substantial improvement over U.S. Pat. Nos. 2,756,906, 2,765,816, and 2,799,465 issued to C. F. Carter and manufactured by Modern Machine Shop, Inc. of Danville, Illinois. The present invention involves a new apparatus which has a number of specific improved features.